Conventionally, semiconductor memories, such as static random access memory (“SRAM”) and dynamic random access memory (“DRAM”), are in widespread use. DRAM is very common due to its high density with a cell size typically between 6F2 and 8F2, where F is a minimum feature size. However, DRAM conventionally has relatively slow access time. SRAM access time is conventionally an order of magnitude faster than DRAM. Though, an SRAM cell is commonly made of four transistors and two resistors or of six transistors, thus leading to a density of approximately 60F2 to 100F2.
Memory designs based on a negative differential resistance (“NDR”) cell, such as a thyristor cell, have been introduced as a replacement for conventional DRAM and SRAM. A thyristor-based random access memory (“RAM”) may be effective in either or both SRAM and DRAM applications.
Contaminants remain a problem in forming integrated circuits. This problem is exacerbated in silicon-on-insulator (“SOI”) wafers, as some contaminants do not diffuse through the buried oxide layer, and thus remain in the silicon layer used for formation of integrated circuit components.
Accordingly, it would be desirable and useful to provide means to mitigate against harmful effects of contaminants.